The invention relates to recovery of gases and in particular to the recovery of sulphur-dioxide from the water of condensation of flue gases.
With the growing attention being given environmental protection recently, and the increasing attention given acid rain, a surge in effort has been present in looking for better ways to clean or "scrub" flue gases from fossil fuel plants before exhausting them to the atmosphere. In order to clean the flue gases, it is known to use alkaline solutions to wash the furnace gas. This process is expensive and produces its own by-products which must be disposed of properly.
My co-pending patent application entitled "Pollution Control and Heat Recovery,", Ser. No. 639,307, filed Aug. 9, 1984, now U.S. Pat. No. 4,597,433, discloses a method for concentrating the noxious sulphur dioxide in the water of condensation of the flue gases. Once the sulphur dioxide is concentrated in the condensate, the problem of economically recovering it still remains.
In the recovery of sulphur dioxide from the burning of sulphur or sulphides, the prior art teaches the use of organic substances added to the wash water in which the sulphur dioxide is dissolved to increase the apparent vapor pressure of the sulphur dioxide so it could be distilled at lower temperatures. Generally, this type of process has not met with much commercial success.
No matter how inexpensive the original agent may be, some small amount is lost in the enormous flow of waste water. This becomes a large expense when the sulphur dioxide content of the waste water is small.
Secondly, recovering the organic additive from both the waste water and sulphur dioxide itself makes the process and apparatus exceedingly complex. This is indicated by U.S. Pat. Nos. 1,946,489 and 2,185,311. Because the application of complex systems threatens the uninterrupted operation of power plants, they are expensive to the point of not being cost effective.